main/java/com/example/faceapp/MainActivity.java
package com.example.faceapp;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import com.google.firebase.database.FirebaseDatabase;

public class MainActivity extends AppCompatActivity {
    private Button button2;
    private Button button3;
    private Button button4;
    private Button button5;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        button2 = findViewById(R.id.button2);
        button3 = findViewById(R.id.button3);
        button4 = findViewById(R.id.button4);
        button5 = findViewById(R.id.button5);

        button3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                open_register();
            }
        });

        button5.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                open_view();
            }
        });



    }

    public void open_register(){
        Intent intent = new Intent(this,MainActivity3.class);
        startActivity(intent);
    }
    public void open_view(){
        Intent intent = new Intent(this,MainActivity2.class);
        startActivity(intent);
    }

}